In recent decades civilization's millennia-long search for clean, safe drinking water has become much easier with modern purification methods. Today, there are few places in the United States without adequate access to potable water. And about three-fourths of the nation's tap water systems add fluoride, credited with helping to reduce tooth decay over the past half century.

But in recent years some have voiced concerns about the safety of tap water and popularizing an alternative: bottled water. Manufacturers of bottled water routinely market their products as safer and healthier than what comes out of your faucet.

But is that true? A few years ago a non-profit consumer organization called the Environmental Working Group (EWG) performed a detailed, comprehensive study of bottled water. Here's some of what they found.

Lack of transparency. It's not always easy to uncover bottled water sources (in some cases, it might actually begin as tap water), how it's processed, or what's in it. That's because unlike water utilities, which are rigorously monitored by the Environmental Protection Agency (EPA), the Food and Drug Administration (FDA) oversees bottled water production with less strenuous guidelines on labeling. Eight out of the top 10 selling brands were less than forthcoming about their water's contents in EWG's investigation.

Higher cost. According to the EPA, the average consumer cost in the last decade for tap water was $2.00 per 1,000 gallons (0.2 cents per gallon). The retail cost for even bulk bottled water is exponentially higher. It can be a costly expenditure for a family to obtain most of their potable water by way of bottled—while still paying for tap water for bathing and other necessities.

Environmental impact. Bottled water is often marketed as the better environmental choice. But bottled water production, packaging and distribution can pose a significant environmental impact. EWG estimated the total production and distribution of bottled water consumes more than 30 million barrels of oil each year. And disposable plastic water bottles have become one of the fastest growing solid waste items at about 4 billion pounds annually.

While there are credible concerns about tap water contaminants, consumers can usually take matters into their own hands with an affordable and effective household filtering system. EWG therefore recommends filtered tap water instead of bottled water for household use.